Hi, I have a recurring problem with the running of my Audi 80 2.0 16v ACE engine. It ended up in a no-start condition and ended up at the garage. The garage correctly diagnosed a worn distributor rotor, replaced it and sent me on my way.

After a few days my original symptoms have returned - Easy to start but hard to keep running from cold. If I let t cut out before it reaches (say) 90 degrees then it will cut out. Then the hard will be very hard to start!. If I can keep it running at 2k rpm for 15minutes then the car suddenly runs well! It really seems like it is temperature dependent or that the engine is warm enough to expel moisture.

I am going to take a look at the rotor and cap again. And potentially replace as a set from BERU.

What (temp) sensors kick in at warmer temps that may have an impact on running?

Other notes:
- Repaired Cyl 1 spark plug lead that had corroded
- Vagcom say 00537 Lambda sensor intermittent error (but I have had this code for years and replacement didn't change anything)
- I have adjusted the MAF with the 3mm hex key. Basically to smooth out idle, I did this with Vaccom live data running -> seems to work well.

Codes:
00537 - lambda (oxygen sensor) regulation
08-10 - Control limit surpassed - Intermittent
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Which sensor does the ECU use - I am getting decent readings on Vagcom and on the instrument dials (oil temp & coolant temp).
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Spark plugs are about 18 months and are correct NGK. They are sooty if the engine is cold/barely starting. From memory the cyl 4 was sootiest - same as csv...They are light brown when running well/engine warm.
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All injectors are "new" (18 months) with new seals. The cold start injector is old. I disconnected it on the way home from work slightly harder to start but it ran with no hesitation, smoother power delivery. I will try this again tomorrow morning when the engine is properly cold.
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Thanks so much, I will report back.

EightyWayNeeds to get out more

Joined: Jul 17, 2014
Posts: 125
Location: Ireland

Posted:
Thu Sep 21, 2017 7:55 am

Update: Removing the cold start connector did not have any effect other than making the car harder to start. The car cut out as it did before. I got it running by keeping it at 1500rpm until warm/hot then it was fine.

I am curious about the ECM temp sender and associated systems. It seems like the car runs ok when it hits closed loop 75°(?) but the cold start setup isn't quite right.

I will take a look at the new distributor rotor to see if it has mangled itself within a week. The mechanic says the cap is ok (otherwise it would have been replaced). Timing was adjusted from 8° BTDC to 6° BTDC which he said was better - but that has made no difference to the cold start issue.

Regarding the ECU Temp sender: I cleaned the connectors (at 6AM!) - I am thinking that Vagcom can see these values and be able to see if the data is off or inconsistent when cold. Or would disconnecting the ECM temp sender bypass that part of the system?

Mikes2Site Moderator

Joined: Jan 31, 2003
Posts: 9137
Location: Polmont

Posted:
Thu Sep 21, 2017 8:16 am

It was worth a try with the csv. It eliminates it as a possible problem. Harder to start and still running like a dog from cold - do you have the facilities to measure the fuel pressures ?

the G62 sender is on the rear of the cyl head on 5 cylinders. Not sure on the 16v, would have to dig out the manual.

Ok, the mechanic said it was the ISV, but the car was behaving in his presence. Fortunately, I had a spare with me when I went to collect the car, tried it, and, no improvement. But, now we could reproduce the problems. After some testing on the ignition/spark system we concluded we did have spark but not as strong as it should be. Fortunately i had a spare coil, fitted it and still the no-start issue continued, but with a stronger spark.

The spark plugs weren't wet after cranking which got him thinking of fuel. With the 3mm hex key in the airflow meter we were able to move the airflap to invoke a start.

My focus is now in 3 areas:
1. The multifunction sensor/thermo - apparently the ECU gets a signal from this one and may be used as part of the cold start fueling system. If the ECU gets its feed from G62 I would consider that too. I have a spare so I test the multifunctional first running a live data feed from vagcom.
2. The metering head may have some internal issue. The Airflow meter is fairly new with a new potentiometer. - possible rebuild using new seals or 2nd hand replacement. I may do measurements on the potentiometer to see if ti falls within spec.
3. The differential pressure regulator sensor on the metering head may also be a culprit. I will research how to diagnose this. I am not sure if it can be replace or if I can get the part.

I think I have something to work with. The problem can be reproduced and manually fixed (by pulling up the air flap). We need this to work automatically as part the cold start system.

Any comments or thoughts/questions are welcome!

Last edited by EightyWay on Mon Sep 25, 2017 8:24 am; edited 1 time in total

EightyWayNeeds to get out more

Joined: Jul 17, 2014
Posts: 125
Location: Ireland

Posted:
Mon Sep 25, 2017 8:22 am

This morning he car was very rough until it hit 90°. Any throttle input would cause it to stall. Then, as it reached 90° it smoothed out. I was running a live feed. I think I need to get a full understanding of the cold start systems on the 16v ACE engine.

After warmup this morning I got this code. I cleared it but it came back immediately. Maybe I have 2 duff ISVs - but they work fine when the engine is warm I've tested them with a multimeter and a 9v battery and they work fine.

00533- Idle Speed Regulation
10-00 - Adaptation Limit Not Reached

Mikes2Site Moderator

Joined: Jan 31, 2003
Posts: 9137
Location: Polmont

Posted:
Mon Sep 25, 2017 7:16 pm

That's the controller for the idle. Sounds like it's operating outside it's normal range so it can't regulate.

It hasn't thrown up any codes since with respect to the idle. It may be something that is happen only on the cold start cycle.

It has become clear that it is going to find someone with the diagnostic expertise to troubleshoot the Motronic. I have seen many forum threads describing the same symptoms unfortunately users never came to a resolution.

I believe it is possible to diagnose it, with time. With a (oldtimer mercedes) specialist on the other side of the country quoting €70 per hour labour I feel that it will cost more than €500 to diagnose (based on the amount of tests that need to be performed). I could swap a load of parts for that!

As it is my only car I need it running so my plan is to get something else and repair it in my own time. I am determined to get to the bottom of this!

Let me know if you know of any CIS/Bosch diagnosis experts in Ireland!

EightyWayNeeds to get out more

Joined: Jul 17, 2014
Posts: 125
Location: Ireland

Posted:
Mon Oct 02, 2017 8:04 am

Update: From what I can gather CIS systems which use sensors also have a "limp mode" when the sensors are disconnected. As mentioned earlier in thread I disconnected the CSV with no effect, I also had the car running without the ECM coolant sensor connected. The differential pressure regulator is last on the list.

My current thinking is that the seals in the metering head are shot. I had been plagued by a Lambda error for year as soon as the engine reaches closed loop. There has been a notable degradation in the running of the car since April.

My initial thought was to get/buy another metering 2nd hand unit. But, there are seal kits available, or even refurbished units. I'm inclined to go for the seal kit.

Watching your thread with interest as i also have an ACE engine in my coupe. Ref your comment on the limp home mode. I found this in my Bentley Bosch fuel injection & engine management. Hope it helps with your KE Motronic CIS.
Limp home mode.
"The actuator plate is designed to rest at a limp home position if the control unit current is interrupted. the engine will continue to run , but slightly leaner than normal. in this circumstance mixture is determined solely by the mech. metering of the air-flow sensor and control plunger. the uncontrolled plate in the pressure actuator allows just enough pressure drop to keep a warm engine running. the engine may not start but if its running , will get you home. you can simulate the limp home home condition on a running warm engine by disconnecting the pressure actuator connector."
Tried to attach a PDF of the page but would not work!

EightyWayNeeds to get out more

Joined: Jul 17, 2014
Posts: 125
Location: Ireland

Posted:
Mon Oct 02, 2017 12:30 pm

Thanks, I might just have that 204 page pdf! One thing I have on my side is a working scantool. Each sensor throws a code when disconnected. I am working with the assumption that the ECM is good and that the wiring to and from the sensors is good.

EightyWayNeeds to get out more

Joined: Jul 17, 2014
Posts: 125
Location: Ireland

Posted:
Mon Oct 02, 2017 7:33 pm

OK, I took some measurements of the various sensors/valves on my CIS ACE engine. Some measurements were taken when the engine was warm. Yes it was a pig to start again but ran ok after 20 minutes after carefully nursing the throttle. There is something very wrong with the open loop cold start setup. Because I don't entirely understand the Motronic CIS I am reluctant to target the fuel distributor.

As far as I can gather there is nothing wrong with these parts. I didn't try to invoke "limp mode" I read that it could be done only when the engine is running and that it may not start without it plugged in.

EightyWayNeeds to get out more

Joined: Jul 17, 2014
Posts: 125
Location: Ireland

Posted:
Tue Oct 03, 2017 8:15 am

OK...the accumulator. I have one in my fuel tank P/N 0438170052. There is also a fuel pressure regulator on the metering head. I assume the only way to test these is to pressure test the system.

My understanding would be that if the accumulator was not holding pressure/maintaining a pressurised system then the car may give trouble starting until the system is pressurised (in my case 20 minutes!). Does this make sense. Could I bypass the accumulator as part of my diagnosis?

Is there anything I can learn from my symptoms which could indicate an accumulator?
- long crank cold start or no start
- rough when cold
- ok when hot

EightyWayNeeds to get out more

Joined: Jul 17, 2014
Posts: 125
Location: Ireland

Posted:
Tue Oct 03, 2017 9:28 pm

RESOLVED:

I had a clear plan of action this evening. Definitively rule out the ECM coolant sensor and do what tests I could on the accumulator/metering head.

Oddly the car started 1st time - actually I wanted long cranking this time! I hooked up Vagcom to clear some codes. On the live data I saw no feed from the differential pressure regulator (turquoise blue in my case). I always assumed that was the unit on the metering head.

Anyway, I decided to measure the resistance of the ECM coolant temp sensor. I could get 5v control voltage from the connector. It was a challenge to get the probes in there, I thought I couldn't get a connection but I didn't know for sure. I connected and grounded the replacement sensor. It ran...with no stutter. Switched the connector back a few more times to confirm the new sensor was better. I bit the bullet and set about removing the sensor. Not to bad in the end with a deep socket 19mm, swivel and a short ratchet. Luckily the heater was off and almost no coolant came out.

Measuring the old and new sensors confused me. Both were 1720 Ohms. So the old was good.....After a bit of head scratching I measured again and again and realised that most of the readings measured 0 and I was getting reliable readings from the new sensor. So I fitted the new one.

All along Vagcom would throw a G62 code if unplugged. It did not detect a fault with the failure of this Bosch sensor.

I ran the car in open loop for a bit to check on my persistent Lambda 00537 code. Nothing so far, touch wood!

I'll bet my airflow settings are a bit off and in the future I may well need to optimise the fuel system - but measurements and test procedures first!

I'm glad I took the time to diagnose, even if it was chaotic. Thanks for the support.

Moral: Find your ECM coolant sensor (seems to vary where it is) and test it - then test it again. It's only €5!

Mikes2Site Moderator

Joined: Jan 31, 2003
Posts: 9137
Location: Polmont

Posted:
Wed Oct 04, 2017 10:45 am

Glad you got there.

The old is possibly cracked and is water contaminated - that's the usual fail mode

Yeah, I got stuck on a roundabout during rush hour this morning. I was pumping the throttle so hard it broke off! The car was similar to before running really rough at cold. At the roundabout I was cranking and as if it was half starting. It was also smoking from somewhere near the bellhousing! It sounded terminal. I got a tow to a nearby petrol station. I fixed throttle cable with zip ties. Got the spare battery and jumped the connection. Sprayed some starter fluid into the air intake and jiggled the engine sensitive connectors a bit, including the hall sensor under the dizzy.

It started 1st time and super smooth/no stutter.

The coolant sensor was a fix, there is no doubt in my mind about that because the car simply runs better. I have question marks about:
- Intermittent electrical connectors, Hall, Coolant temp ecu
- The settings on the metering head/mixture (hex 3)
- Fuel pressure/fuel starvation

It's looking like it won't be practical to run this car daily

EightyWayNeeds to get out more

Joined: Jul 17, 2014
Posts: 125
Location: Ireland

Posted:
Thu Oct 26, 2017 8:45 am

So I came back from 2 weeks away. The car is in a no-start condition. Interesting is that there appears to be some form of detonation at random moments (this might be the correct description).

It manifests itself by pressure being fed back through the air intake into the boot between the airflow flap and the throttle body. It expands wth quite violent pressure and even some fumes (exhaust) come can escape out from the boot. Added, a similar phenomenon happens through the exhaust with occasional burps of pressure. It smells like a fuelly smoky mix.

You can imagine that the airflow flap gets forced down which I need to pull up to release. It feels a little jammed. Any ideas?

EightyWayNeeds to get out more

Joined: Jul 17, 2014
Posts: 125
Location: Ireland

Posted:
Fri Oct 27, 2017 7:58 pm

So, I had another go today. Same old no-start. I was lazy and didn't tighten the clamps on the michelin man intake boot. I had sprayed starting fluid into the intake. The boot blew straight off and the fluid caught fire! Can someone explain to me what is going on? Have the laws of combustion suddenly changed?

On another note, I viewed a skoda octavia last night. Using vagcom I priced the three common faults - it ended up at €3K. Worst case scenario for the audi is a metering head which is only €300 refurbed. So this weekend is fuel pressure measuring time!

Fuel pressure tests were a disaster. Leaks went everywhere, returning the kit! Next step is a visual inspection of the metering head and determining if the plunger is functional.

EightyWayNeeds to get out more

Joined: Jul 17, 2014
Posts: 125
Location: Ireland

Posted:
Sat Nov 18, 2017 11:13 am

So my next step is changing the diapraghm in the fuel distributer. I'd rather not spend €300 on a rebuild without knowing 100%. If it is perforated at least it will be an improvement. I'll clean as much as possible without completely disassembling. At the end of the day this is a guess!

EightyWayNeeds to get out more

Joined: Jul 17, 2014
Posts: 125
Location: Ireland

Posted:
Mon Dec 11, 2017 10:58 am

Ok, so I replaced the membrane in the fuel distributor. I didn't use gasket seal to stick it in place as some guides suggest. I also had queries about my Airflow meter which I may have gone out of spec, but swaped with a known working unit! I also swapped the fuel pressure regulator whilst I was at it (unknown origin) - all free.

...AND no-start. But after some serious cranking it just barely spluttered into life. I tried to nurse it until it got warm but failed (I had it running for 20 minutes). I couldn't let the car drop below 2k rpm.

So the car is exactly the same as before all of my metering head swaps. Which is good and bad news. I didn't conclusively prove that any of the parts were faulty. There are a few parts on the fuel system which haven't been addressed like the in-tank accumulator, and the differential pressure regulator and cold start valve.

General logic would suggest looking at the sensors that the ECU uses and inputs and outputs when cold. The impulse sender on cyl 4 springs to mind.

I also have queries about my "weak spark" still and the root cause of my distributor rotor mangling itself in September.

Is there anyone out there in Ireland who could take a look at it? I'm really struggling.

The car ran but could cut out easily - like releasing the throttle suddenly or even using the power steering! The car was hunting at idle.

I did a hack fix by adjusting the fuel mixture out of spec (triggering a 00533 idle code) but the idle was then solid at 1000rpm. I believe this forces the ISV open. The downside is that it is spitting out plenty of carbon deposits.

I have yet to puzzle out exactly what this all means. I need to go back to my research on the Motronic, however I believe I need to look at the sensors that regulate the ISV. Thinking of these off the top of my head:

Added to the last message, the audi is spitting of piles of smoke. So much so that there is a nice soot deposit on the wheelie bin sitting behind the exhaust. I put it down to an incorrect air fuel mixture.

A friend mentioned that it might be Piston rings. I haven't seen much threads on piston rings on the ACE/ABF 2.0 16v engine. Most threads seem to redirect people to investigate the valve stem seals first. My smoking Audi doesn't seem to satisfy the criteria for either the valves or the rings. I'd like to rule them out though.

I noted 150psi on 3 cylinders and 130psi on one of the cylinders - what does that tell me?

I'll redo the test in the weekend.

EightyWayNeeds to get out more

Joined: Jul 17, 2014
Posts: 125
Location: Ireland

Posted:
Tue Jan 30, 2018 5:08 pm

Compression is up! Engine was cold in no-start condition.

Front to back
Cyl 1: 175psi
Cyl 2: 200psi
Cyl 3: 200psi
Cyl 4: 200psi

Comment: the plugs were fouled with soot, maybe soot in the bores gave the higher reading.

Fuelling:
I removed the plugs - they were covered with soot as I was expected. But the plugs were very wet.

Spark:
I removed the fuel pump fuse. Removed each plug and tested for spark (with a tester). Each spark fired. The spark was weak, as noted earlier in the thread. It was also a bit random or inconsistent. Each plug was firing in the same way.

Air
Next: I measured the Airflow potentiometer (target between 4.35-5.35v) 4.84v All good

Differential pressure regulator current 65.7mA (ignition on but engine off for KE3-jetronic and KE-motronic - 90 - 120 mA) This seems out of spec.

My sense is that the spark is insufficient and/or incorrectly timed. By chance I have been able to get the car running in the past but it ran like hell.

Historically (timeline since 1st problem) it was the coil, the second time it was the dizzy rotor. Then I found a perished spark lead connector. The mechanic said he did the timing but I think I should be looking in this space. The mechanic put a crack in the case of the dizzy cover (but only at the bolt hole). The cover seems clean, as is the new rotor. I have run the car since as well.

Next steps:
1. Check resistance of spark leads
2. Test coil output - Anyone know how to do this? I am looking at both intensity and frequency.

Question: the previous owner cut the cable to the coil so they could use a cheaper coil. I swapped it back to stock with a used unit. I soldered the joins - could that cause problems?

3. Timing - I really can't find the marks on the flywheel. any tips welcome!

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